Vector fields implicitly contain a large amount of data not directly nor easily observable. In engineering applications, vector fields can represent magnetic, electrical, fluid and gas velocity fields as well as various displacement and strain fields. Several techniques exist in computer graphics to assist scientists and engineers in understanding the phenomena behind the analyzed data. One technique called streamlines creates trajectories of massless particles that move along the field. The trajectories are generated using standard techniques by solving differential equations that have right side derivatives equal to the sample vectors of the vector field under investigation.
Another technique called hedgehogs represents the vector field by drawing oriented scaled lines along the vectors of a vector field. Most techniques, except hedgehogs, require the solution of differential equations to generate the appropriate imagery. The solution of differential equations can be time consuming, especially if the original field data is given on a non-structured grid. In the case of the hedgehog technique, the graphics representation is simple and fast. However, if the field data is sampled at more than a few hundred points in the 3-D space, its visual representation on a 2-D computer display can be difficult to understand. If particles are used to simulate the motion along the streamlines, the efficiency of the technique is drastically reduced as the number of particles increases. Another drawback of techniques relying on streamlines is the computational errors that increase with the length of the trajectories. This can produce misleading and inaccurate representations.
In computer graphics, color, texture, and transparency are usually used to enhance visual perception of displayed images. For example, vectors in the hedgehog method can be colored differently based on the vector length. Transparency and texture are more often used to display surfaces and solids. Transparency allows one to view simultaneously two or more objects, one in front of the others. Texture is typically used to present naturally looking surfaces when they simulate real life objects such as wood, grass, buildings, etc., and also to enhance motion perception when one object is moving in front of another. In the last case, texture provides an additional frame of reference for local motion detection.
In the past, one application of color in computer graphics has been to indicate movement and velocity. This has been done through the use of color map cycling. The technique relies on the ability to quickly update a hardware color map to produce the effect of movement in a still raster image. Current graphics supercomputers typically do not rely on color maps to generate screen images, but they do have the ability to perform texture mapping. This ability can be utilized in a similar manner to color map animation, with additional benefits.